This invention relates to a composition and method of making a seal in a liquid crystal display cell. More particularly, the invention relates to a composition and method of fabricating a plastic seal for liquid crystal display cells wherein such seal has the advantages of being transparent, hermetic, and relatively chemically inert to the liquid crystal materials utilized in such display cells.
In fabricating liquid crystal display cells it is common to utilize planar glass plates spaced apart by a small distance and having a seal formed about the outer periphery thereof to form a hermetically sealed cell for confining the liquid crystal material. It is desired that the seal, upon formation, be transparent, hermetic, and relatively chemically inert to the liquid crystal materials used in such displays. Conventional methods of fabricating liquid crystal display cells have been employed in the prior art comprising glass frit. The use of glass frit, however, requires a relatively high temperature around 900.degree. F to effect a hermetic seal, and in cell designs wherein surface rubbing or other treatment of the glass plates is necessary to obtain alignment of the liquid crystal materials within the cell, such temperatures tend to efface the alignment. Accordingly, glass frit seals have not been entirely satisfactory for fabricating liquid crystal display cells.
A variety of organic sealing materials, such as epoxies, urethanes and polyesters have also been used in the prior art for forming such seals. However, these materials are disadvantageous for forming such seals since they tend to deteriorate under conditions of moderate or high humidity. In addition, the liquid crystal materials are effective solvents for many of such organic sealing materials. Accordingly, the liquid crystal materials tend to react with the sealants and the resulting contamination results in degradation of the liquid crystal materials, thereby tending to reduce the useful life of the display cell.
Accordingly, it is an object of the invention to provide a composition and method of making the seal in a liquid crystal display cell wherein planar glass plates are bonded together to form a satisfactory hermetic seal.
It is another object of the invention to provide a composition or method of making a seal in a liquid crystal display cell which does not deteriorate in the presence of high humidity.
It is yet a further object of the invention to provide a composition and method of making a seal in a liquid crystal display cell wherein the sealant does not react with the liquid crystal material or provide contamination to the display cell.